This invention relates to die cutting machines. In particular, the invention relates to die cutting adapted to cut patterns from sheet material such as veneers, boxboard, plastic sheeting or any material in sheet or strip form.
It has previously been known to cut sheet material using dies mounted on clam shell or reciprocating presses. Due to the essentially uniform contact between the work piece and the dies, the operation of the machine is limited by the size of the cut. Essentially, increasing the linear distance of the cut requires successively more power due to the essentially uniform or all at once operation of the cut.
To overcome these limitations in reciprocating and clam shell presses, the industry has turned more and more to rotary die cutting systems, that is, those systems which can apply a differential pressure to the die by incrementally cutting the strip or sheet as it is passed underneath the die and over a supporting anvil. Since the cutting is progressive, the machine is not as restricted to the linear size of the cut or die which is used.
U.S. Pat. Nos. 3,808,925; 3,965,786; 4,182,208; 4,455,903 exemplify rotary die cutting systems for sheets and strips. The disclosures of the above patents are incorporated by reference herein.
While rotary die cutting systems offer the possibility of incremental or differential cutting of the die into the work piece, and thus are not as limited in the size of the cut which can be used, the increasing linear size of a cut does impose some problems. Particularly, when a large cut must be made transverse to the direction of travel of the work piece through the die. Such large cuts require a significantly greater incremental force applied to the die. This greater force which is required must be generated at the die and, of course, ultimately is transmitted to the die through the drive train of the die cutting system from the prime mover. The drive train and mechanism of the die cutting must be sufficiently strong to withstand the shock imposed by the sudden incremental force required and the drive train and prime mover must be strong enough to develop and transmit that force. As will be appreciated, these components of the system must either be over designed to tolerate this shock of incremental force or the entire system risks failure as a result of breakage of the drive train and prime mover.
It is an object of this invention to provide a rotary die cutting system which effectively cuts sheet material.
It is a further object of this invention to provide a rotary die cutter which can effectively cut large lineal distances and maintain the register of the system.
It is a further object of the invention to provide a rotary die system which does not require an over design of the drive train and prime mover and which minimizes shock to those components when instantaneously making long lineal cuts.
It is a further object of this invention to provide a rotary die cutting system which can apply a reduced shock force.
The invention will be further understood from the following Description of the Drawings and Description of the Preferred Embodiments.